1. Field of the Invention
This invention pertains generally to sterilization methods, and more particularly, to a method and apparatus for sterilizing organic and inorganic matter in a non-liquid environment using a combination of ultraviolet light and ultrasonic waves.
2. Description of the Background Art
The effective removal of viable pathogenic microorganisms is essential to those who regularly come into contact with potentially infectious microorganisms. Medical care givers, such as physicians, nurses, emergency medical technicians, and dental care givers, such as dentists and oral hygienists, are frequently exposed to bodily fluids which may contain infectious microorganisms, such as viruses, bacteria, etc. Instrumentation (including human hands) must be effectively sterilized to prevent the transmission of potentially infectious microorganisms between patients and to the workers themselves. Microbiological researchers are constantly handling potentially infectious microorganisms as a regular part of their responsibilities and require effective and frequent sterilization of instrumentation and hands to protect themselves and their co-workers from such undesirable exposure.
People working in the field of food processing, packaging and service also have an essential need for the effective removal of potentially infectious microorganisms from a variety of food surfaces and the various equipment used in handling and processing. As part of their jobs, these workers are required to handle a variety of raw meats, poultry, seafood, baked goods, and vegetables for processing, packaging, delivery and sale to the general public. Food service workers are required to handle and prepare food products that are often to be consumed shortly thereafter by the public. Raw meats, poultry and seafood, especially, are ideal sources for the incubation and multiplication of undesired and potentially infectious microorganisms. The workers' equipment and hands must be effectively sterilized on a frequent basis to prevent infecting themselves or spreading microorganisms from a contaminated source to the rest of the supply, and thus subjecting the general public to the risk of exposure.
Similarly, there is a need for effective removal of potentially infectious microorganisms from a variety of medical and dental instruments and devices that cannot be effectively sterilized by other conventional means such as autoclaving due to their internal electronic nature. These instruments and/or devices are often used on patients where infectious microorganisms that are present on the surface of the instruments and/or devices may be transmitted onto (or even into) the patient being treated if not effectively sterilized prior to its intended use, which can cause potentially life threatening conditions.
Food products available for public consumption also require effective removal of potentially dangerous microorganisms prior to consumption by the general public. As discussed above, handling of food products by workers with non-sterilized hands can result in the spread of undesired microorganisms, or conversely, direct contact of food products with contaminated food processing and packaging equipment can also result in the spread of unwanted microorganisms.
A commonly used method for sterilizing the hands of medical, dental and food service workers is repeated washing and/or scrubbing of the hands. This procedure can be time consuming as it must be repeated frequently after the worker comes into contact with a potentially contaminated source. Also, this method may not effectively sterilize the worker's hands due to ineffective washing techniques, types of cleaning agents used, or even the length of time spent physically cleaning the hands. Constant, repetitive hand washing can also damage the skin due to use of soaps, detergents and the actual scrubbing actions that remove the skin's natural oils and can leave the skin dehydrated and irritated. The disadvantages of excessive time consumption, non-thorough hand sterilization, and skin irritation may cause the worker to avoid the frequent hand washing required to effectively prevent the spread of potentially infectious microorganisms.
Medical and dental instruments and devices are commonly sterilized via use of steam autoclaves and other methods that incorporate the use of heat, steam, gamma radiation, electron beam, and/or chemical agents to remove viable pathogenic microorganisms. However, the effectiveness of these methods varies and they typically require the use of expensive, sophisticated equipment and generally involve a substantial amount of time to complete. Also, some instruments and devices are particularly sensitive to high temperatures, moisture, gamma radiation, electron beams and/or certain chemicals being used, and cannot survive these methods of sterilization. Therefore these instruments, in particular, require other methods of sterilization.
The use of ultraviolet light is another method used to sterilize organic and inorganic matter. Exposure to certain ultraviolet light band wavelengths has been discovered to be an effective means of destroying microorganisms. In using this method of sterilization, the user places the object or device to be cleaned into a chamber to expose the device or object to be cleaned to a prescribed dose of ultraviolet light. The interior of the cleaning chamber is usually coated with a reflective surface which reflects the light to ensure that all surfaces of the object being sterilized are irradiated with a sufficient amount of the ultraviolet light. The amount of time required for an adequate dosage of the ultraviolet light varies but typically requires at least ten seconds. However, the use of ultraviolet light for microbiological sterilization of organic and inorganic surface matter has historically been abandoned in favor of more sophisticated methods that employ heat, steam, gamma radiation, electron beams, and/or chemicals. This may be a result of manufacturers' desire to offer more expensive sterilization devices in lieu of simplified technology. Typically, the use of ultraviolet light has been relegated to the treatment of air and/or water, which is generally circulated past the ultraviolet light source in a cabinet or the like and then into the sterilization environment.
Other sterilization methods involve the use of ultrasonic waves which resonate through an aqueous solution in which the item to be sterilized is immersed either partially or completely. The ultrasonic waves within the aqueous solution cause zones of compression and vacuity which act physically on the object placed within the aqueous solution causing foreign substances thereon to be dislodged and dispersed within the solution. When the object to be sterilized is a human hand, for example, the aqueous solution employed must be compatible with human skin, thus limiting the types of available aqueous solutions which can be used and which are effective. Furthermore, because the hands have to be immersed into an aqueous solution to utilize this sterilization method, the hands become saturated with the aqueous solution and must thereafter be dried off. The hand drying process usually entails convecting air over the skin surface for a period of time until the hands are sufficiently dry. This consumes time and may even leave the skin dehydrated. If the item to be sterilized is some other organic material, such as meats, poultry, seafood or vegetables, immersing the item into an aqueous solution can damage or even destroy its properties, thus rendering the food product useless. Similarly, certain medical instruments and devices that need sterilizing become inoperable when they are immersed in an aqueous solution. These instances illustrate the need for a sterilization method which can effectively, frequently, and quickly sterilize organic and inorganic matter in a non-aqueous environment.
There are also sterilization methods which combine the use of both ultraviolet light and ultrasonic waves; however the ultrasonic emitting step is performed in an aqueous solution. Using this method, an ultraviolet light source is positioned to irradiate a cleaning liquid in a cleaning tank into which the item to be sterilized is immersed. A piezoelectric transducer agitates the liquid ultrasonically causing both microscopic and macroscopic agitation, which dislodges foreign substances from the surface of the item. Because the ultraviolet irradiating step occurs concurrently with the ultrasonic process, the microorganisms dislodged from the item being sterilized is subjected to the ultraviolet light, thereby destroying the microorganisms. In these combination methods, the disadvantages associated with each step previously mentioned still exist.
Therefore a need exists for a method to sterilize organic and inorganic material in a non-liquid environment using a combination of ultraviolet light and ultrasonic waves. The present invention satisfies those needs, as well as others, and overcomes the deficiencies in prior technology.